Those skilled in the art of diagnosing cardiac ailments have long understood that certain patients, in particular heart failure (HF) patients, suffer uncoordinated mechanical activity wherein the myocardial depolarization and contraction of the atria and ventricles (i.e., right and left) occur in an uncoordinated fashion. Such uncoordinated motion can cause a decrease in stroke volume and/or cardiac output (CO), among other detrimental effects. Recently a variety of techniques have been proposed and practiced for minimizing such uncoordinated motion.
These prior art techniques for minimizing uncoordinated myocardial motion include CRT optimization. One known way to attempt to optimize CRT delivery involves Doppler echocardiographic imaging of ventricular contractions while adjusting interventricular pacing stimulus delivery (i.e., V-V timing). The optimized V-V timing is the interventricular timing that produces the least amount of visibly perceptible dyssynchrony. For successful CRT delivery, the A-V intervals typically are programmed to a magnitude less than the intrinsic atrial-to-ventricular (P-R) interval for a given subject to help ensure bi-ventricular CRT delivery.
An apparatus for delivering CRT includes implantable pulse generator (IPG) with or without high-energy cardioversion/defibrillation therapy capability. An IPG adapted for CRT delivery typically includes three medical electrical leads coupled to myocardial tissue. A first lead typically coupled to the right atrium, a second lead typically coupled to the right ventricle, and a third lead typically coupled to the left ventricle (often via the coronary sinus or great vein). That is, the third lead couples to a location on the free wall of the left ventricle.
Thus, as is known in the art, based at least in part on acute echocardiographic measurement an IPG configured for CRT delivery provides only a limited ability to adjust operative A-V and to a slightly greater degree, V-V intervals. Thus, a need exists in the art for appropriately optimizing electrical cardiac pacing stimulus delivery between the atria and the left ventricle (LV) and/or the right ventricle (RV) in an effort to enhance hemodynamics and other benefits of optimized pacing therapy delivery. When successfully and optimally delivered, certain pacing therapies, such as bi-ventricular CRT, are known to increase CO and may, over time, cause a phenomenon known in the art as “reverse remodeling” of the LV and RV (and/or other beneficial) physiologic changes to the patient's heart.